The present invention is directed to a composition for use in a light directing arrangement and method for use with a display apparatus, and more particularly to a composition that is resistant to corrosion.
Liquid crystal displays (LCD) are used in many different types of electronic devices, including portable computers, cellular phones, and digital watches. An LCD may include a reflector for directing ambient light to the viewer, or a partially transmissive reflector for also allowing light from a light source within the device to convey information to the viewer. A partially transmissive reflector is commonly called a transflector, and an LCD that incorporates a transflector is commonly called transflective. Some examples of LCD devices are discussed in co-pending application, xe2x80x9cOptical Devices Using Reflecting Polarizing Materialsxe2x80x9d, Ser. No. 09/298,003, filed Apr. 22, 1999.
The present invention is to a composition, and a prismatic structure in a display apparatus that utilizes this composition. The composition, when cured to form a structure is generally void of halogenated components yet provides a high index of refraction. Further, the structure provides a good substrate for adhesion of a metal layer thereon. And further, the composition provides protection against corrosion for a metallic layer that may be provided in the display apparatus, particularly a layer having silver therein, either on the prismatic construction or elsewhere in the display apparatus.
The composition of the present invention includes a vinyl monomer, for example, an alkyl styrene monomer such as methyl styrene, and various co-monomers and/or oligomers. In particular, a composition comprises each of bisphenol-A epoxy diacrylate, novolak epoxy acrylate, and a vinyl monomer, which includes alkyl styrenes (for example, methyl styrene). An initiator may be added to provide a free radical source to initiate polymerization of the composition to a polymerized structure.
The composition of the present invention, when provided as a film, may be coated with a metallic layer. The metal layer may be selected from a group consisting of silver, chromium, nickel, aluminum, titanium, aluminum-titanium alloy, gold, zirconium, platinum, palladium, aluminum-chromium alloy and rhodium. The metal layer is preferably silver. In a preferred embodiment, the metal layer is a silver layer having a thickness of about 400 Angstroms.
The composition may be provided as a three dimensional prismatic structure. Typically, the structure has two sides, where one side is substantially smooth and the other has a three dimensional structure, such as saw-tooth formations having tilted surfaces. A tilt angle of the tilted surfaces offsets an optimal viewing angle for the display from a glare angle for the display. In one application, the tilted surfaces of the prismatic layer may have a tilt angle of about 1xc2x0 to 35xc2x0 from horizontal. The saw-tooth formations may have a pitch (i.e., the prism repeat distance) of about 5 microns or more and about 200 microns or less, for one specific application.
A metal layer may be provided on either side of the prismatic structure, although in some embodiments it is preferred that the metal layer is on the side having the three dimensional prismatic formations.
A film of the composition, whether a flat film or a three-dimensional film, may also include a pressure sensitive adhesive layer. The pressure sensitive adhesive layer may be an acrylate acrylic acid adhesive layer, the adhesive layer being preferably optically diffuse.